Inkjet head and manufacturing method of the same

ABSTRACT

A surface electrode is provided on a surface of a piezoelectric element for changing the volume of each pressure chamber in an inkjet head. The surface electrode has a main electrode portion opposed to the pressure chamber and a connecting portion not opposed to the pressure chamber. A land is provided on one end of the connecting portion of the surface electrode. The land is electrically connected to the surface electrode. When the land is connected to a terminal of an FPC, a driving signal can be transmitted to the surface electrode. The land is therefore connected to the terminal using solder and a thermosetting resin covering the surface of the solder, or using only a thermosetting resin.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an inkjet head for ejecting inkonto a record medium to print, and also to a manufacturing method of theinkjet head.

[0003] 2. Description of Related Art

[0004] An inkjet head used in an inkjet printer includes therein an inktank and pressure chambers. Each pressure chamber is supplied with inkfrom the ink tank. When a piezoelectric element provided above apressure chamber is deformed to change the volume of the pressurechamber, pressure is applied to ink in the pressure chamber so that theink is ejected through a nozzle connected to the pressure chamber. Todeform the piezoelectric element, in general, a driving signal issupplied to a surface electrode provided on a face of the piezoelectricelement opposite to the pressure chamber. An electric field is therebyapplied to the piezoelectric element. The surface electrode is connectedto a terminal on a printed circuit board such as a flexible printedcircuit (FPC). The driving signal is supplied to the surface electrodethrough the printed circuit board from a driver IC connected to theprinted circuit board.

[0005] In general, electrical connection between the terminal of theprinted circuit board and the surface electrode is realized in themanner that solder interposed between the terminal and surface electrodeis melted with heat (see JP-A-7-1566376). Besides, there is known amethod using no solder (see JP-A-8-156252). In the method using nosolder, a printed circuit board is prepared on which two films are putin layers. The lower film has a cut-out portion larger in area than thesurface electrode. A terminal smaller in area than the surface electrodeis provided on the lower face of the upper film within the cut-outportion of the lower film. After a conductive adhesive is dropped on thesurface electrode, the terminal is pressed onto the surface electrode sothat they are electrically connected to each other. The connectingportion between the terminal and the surface electrode is at a positionopposite to a pressure chamber.

[0006] In the above technique using solder for electrically connectingthe terminal of the printed circuit board and the surface electrode toeach other, however, the solder having melted with heat to have highfluidity may move into a region on the surface electrode opposite to thepressure chamber. In this case, deformation of a piezoelectric elementupon ink ejection may be hindered due to the rigidity of the solder.This causes deterioration of ink ejection performance. To avoid this,for example, such a measure is taken as elongating distances betweenneighboring connecting portions of the terminal and the surfaceelectrode, however, this is contrary to high integration. Furthermore,in case the surface electrode is made of metal, the surface electrode iseasily diffused into solder when the solder adheres to a surfaceelectrode. This may cause rise of the resistance between the surfaceelectrode and the terminal, and at worst, electrical braking may happen.

[0007] In addition, when surface electrodes corresponding to therespective pressure chambers are connected to terminals corresponding tothe respective surface electrodes, solder having melted to have highfluidity may cause a short circuit between neighboring connectingportions.

[0008] In the above technique using a conductive adhesive in place ofsolder, because the conductive adhesive is lower in fluidity than solderupon being heated, the conductive adhesive stays within each cut-outportion of the lower film on the printed circuit board. Therefore, theabove-described problems with the case of using solder, such ashindrance of deformation of a piezoelectric element, rise of theresistance, braking, and a short circuit, are relieved in comparison.However, because the connecting portion between the terminal and thesurface electrode is at a position opposite to a pressure chamber asdescribed above, there is a problem that deformation of a piezoelectricelement upon ink ejection is hindered. This makes it difficult to changethe volume of the pressure chamber and thus it causes deterioration ofink ejection performance,

SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide an inkjet headcapable of suppressing hindrance of deformation of a piezoelectricelement, and to provide a manufacturing method of the inkjet head.

[0010] Another object of the present invention is to provide an inkjethead capable of suppressing hindrance of deformation of a piezoelectricelement, rise of the resistance, braking, and a short circuit betweenterminals with suppressing hindrance of deformation of a piezoelectricelement, and to provide a manufacturing method of the inkjet head.

[0011] According to an aspect of the present invention, an inkjet headcomprises an ink passage unit including pressure chambers and aplurality of wall portions defining each of the plurality of pressurechambers; and an actuator unit including a piezoelectric elementdisposed on the ink passage unit, a surface electrode disposed on thepiezoelectric element and having a main electrode portion opposed to apressure chamber and a connecting portion opposed to a wall portion, anda land disposed on the piezoelectric element in a region opposed to thewall portion. The land is electrically connected to the surfaceelectrode. The inkjet head further comprises a printed circuit board onwhich a terminal electrically connected to the land and a predeterminedwiring pattern are provided; and a metallic bond for electricallyconnecting the land to the terminal. The metallic bond is disposed in atleast one of a region between the land and the terminal and a regionextending over the land and the terminal along the peripheries of theland and the terminal. The inkjet head further comprises a protrusiondisposed on the connecting portion.

[0012] According to the invention, because the connecting portionbetween the land and the terminal is in a region not opposed to thepressure chamber, hindrance of deformation of the piezoelectric elementcan be suppressed. Further, because the protrusion is formed on thesurface electrode in a region not opposed to the pressure chamber,movement of the metallic bond, which has been melted to have highfluidity, to a region of the surface electrode opposed to the pressurechamber, i.e., the main electrode portion, can be suppressed Therefore,the problem such as hindrance of deformation of the piezoelectricelement due to the rigidity of the metallic bond such as solder, can berelieved. Also, because adhesion of the metallic bond such as solder tothe surface electrode is suppressed, the problems such as rise of theresistance and braking can be relieved.

[0013] According to another aspect of the present invention, an inkjethead comprises an ink passage unit including pressure chambers and aplurality of wall portions defining each of the plurality of pressurechambers; and an actuator unit including a piezoelectric elementdisposed on the ink passage unit, a surface electrode disposed on thepiezoelectric element and having a main electrode portion opposed to apressure chamber and a connecting portion opposed to a wall portion, anda land disposed on the piezoelectric element in a region opposed to thewall portion. The land is electrically connected to the surfaceelectrode. The inkjet head further comprises a printed circuit board onwhich a terminal electrically connected to the land and a predeterminedwiring pattern are provided; and a metallic bond for electricallyconnecting the land to the terminal. The metallic bond is disposed in atleast one of a region between the land and the terminal and a regionextending over the land and the terminal along the peripheries of theland and the terminal. The inkjet head further comprises a thermosettingresin covering at least part of the metallic bond.

[0014] According to the invention, because the connecting portionbetween the land and the terminal is in a region not opposed to thepressure chamber, hindrance of deformation of the piezoelectric elementcan be suppressed. Further, because the metallic bond is covered withthe thermosetting resin that has fluidity lower than that of a metallicmaterial even by being heated, movement of the metallic bond can besuppressed. Therefore, by adequately determining the part of themetallic bond with the thermosetting resin, the problems such ashindrance of deformation of a piezoelectric element, rise of theresistance, and braking can be relieved, and/or a short circuit betweenterminals can be suppressed. For example, by disposing the thermosettingresin in the connecting portion between the land and the main electrodeportion of the surface electrode, movement of the metallic bond to theregion of the surface electrode opposed to the pressure chamber, i.e.,the main electrode portion, can be suppressed, same as the above aspect.This results in relieving the problems such as hindrance of deformationof a piezoelectric element, rise of the resistance, and braking. On theother hand, by disposing the thermosetting resin between neighboringconnecting portions between lands and terminals, a short circuit betweenthe terminals can be suppressed.

[0015] According to still another aspect of the present invention, aninkjet head comprises an ink passage unit including pressure chambersand a plurality of wall portions defining each of the plurality ofpressure chambers; and an actuator unit including a piezoelectricelement disposed on the ink passage unit, a surface electrode disposedon the piezoelectric element and having a main electrode portion opposedto a pressure chamber and a connecting portion opposed to a wallportion, and a land disposed on the piezoelectric element in a regionopposed to the wall portion. The land is electrically connected to thesurface electrode. The inkjet head further comprises a printed circuitboard on which a terminal electrically connected to the land and apredetermined wiring pattern are provided; and a thermosetting resin forelectrically connecting the land to the terminal. The thermosettingresin is disposed in a region opposed to the wall portion.

[0016] According to the invention, because the connecting portionbetween the land and the terminal is in a region not opposed to thepressure chamber, hindrance of deformation of the piezoelectric elementcan be suppressed. Further, because not a metallic material but thethermosetting resin is used for electrically connecting the land to theterminal, the problems such as hindrance of deformation of apiezoelectric element, rise of the resistance, braking, and shortcircuit between terminals, which may happen in case of using a metallicmaterial, can be relieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other and further objects, features and advantages of theinvention will appear more fully from the following description taken inconnection with the accompanying drawings in which:

[0018]FIG. 1 is a perspective view of an inkjet head according to afirst embodiment of the present invention;

[0019]FIG. 2 is a sectional view taken along line II-II in FIG. 1;

[0020]FIG. 3 is a plan view of a head main body included in the inkjethead of FIG. 1;

[0021]FIG. 4 is an enlarged view of a region enclosed with an alternatelong and short dash line in FIG. 3;

[0022]FIG. 5 is an enlarged view of a region enclosed with an alternatelong and short dash line in FIG. 4;

[0023]FIG. 6 is a partial sectional view of the head main body of FIG. 3taken along line VI-VI in FIG. 5;

[0024]FIG. 7 is an enlarged view of a region enclosed with an alternatelong and two short dashes line in FIG. 4;

[0025]FIG. 8 is a partial exploded perspective view of the head mainbody of FIG. 6 and a flexible printed circuit board bonded to the headmain body;

[0026]FIG. 9A is a plan view illustrating the shape of a space formingan ink passage of FIG. 6;

[0027]FIG. 9B is a perspective view illustrating the shape of the spaceforming the ink passage of FIG. 6;

[0028]FIG. 10A is a lateral enlarged sectional view of a region enclosedwith an alternate long and short dash line in FIG. 6;

[0029]FIG. 10B is a plan view illustrating shapes of an individualelectrode, i.e., a surface electrode, formed on a surface of an actuatorunit, and a land;

[0030]FIG. 11A is a partial sectional view illustrating a state before awork for disposing an epoxy resin on a surface of solder covering aterminal, in a process for connecting the terminal to a land, in amanufacturing method of an inkjet head according to the first embodimentof the present invention;

[0031]FIG. 11B is a partial sectional view, successive to FIG. 11A,illustrating a state wherein the terminal on which the solder and theepoxy resin are disposed, and the land are opposed to each other;

[0032]FIG. 11C is a partial sectional view, successive to FIG. 11B,illustrating a state wherein the terminal and the land are connected toeach other;

[0033]FIG. 11D is a plan view, corresponding to FIG. 10B, illustratingan occupation area of the epoxy resin in the state of FIG. 11C;

[0034]FIG. 12 is a partial sectional view, corresponding to FIG. 11B,illustrating a modification of the manufacturing method of the inkjethead according to the first embodiment of the present invention;

[0035]FIG. 13A is a partial sectional view, corresponding to FIG. 11B,illustrating a modification of the inkjet head according to the firstembodiment of the present invention;

[0036]FIG. 13B is a partial sectional view, corresponding to FIG. 11C,successive to FIG. 13A, illustrating a state wherein the terminal andthe land are connected to each other;

[0037]FIG. 13C is a plan view, corresponding to FIG. 10B, illustratingan occupation area of the epoxy resin in the state of FIG. 13B;

[0038]FIG. 14A is a partial sectional view, corresponding to FIG. 11B,illustrating another modification of the inkjet head according to thefirst embodiment of the present invention;

[0039]FIG. 14B is a partial sectional view, corresponding to FIG. 11C,successive to FIG. 14A, illustrating a state wherein the terminal andthe land are connected to each other;

[0040]FIG. 14C is a plan view, corresponding to FIG. 10B, illustratingan occupation area of the epoxy resin in the state of FIG. 14B;

[0041]FIG. 15A is a partial sectional view corresponding to FIG. 11B, ina manufacturing method of an inkjet head according to a secondembodiment of the present invention; and

[0042]FIG. 15B is a partial sectional view, corresponding to FIG. 11C,successive to FIG. 15A, illustrating a state wherein the terminal andthe land are connected to each other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] First, a general construction of an inkjet head according to afirst embodiment of the present invention will be described withreference to FIG. 1. FIG. 1 is a perspective view of an inkjet headaccording to this embodiment. FIG. 2 is a sectional view taken alongline II-II in FIG. 1. FIG. 3 is a plan view of a head main body includedin the inkjet head of FIG. 1. The inkjet head 1 includes a head mainbody 1 a having a rectangular shape in plane and extending in onedirection, i,e., main scanning direction, and a base portion 71 forsupporting the head main body 1 a. The base portion 71 supporting thehead main body 1 a further supports thereon driver ICs 80 for supplyingdriving signals to individual electrodes 35, i.e., surface electrodes,as illustrated in FIGS. 10A and 10B, and substrates 81.

[0044] Referring to FIG. 1, the base portion 71 is made up of a baseblock 75 partially bonded to the upper face of the head main body 1 a tosupport the head main body 1 a, and a holder 72 bonded to the upper faceof the base block 75 to support the base block 75. The base block 75 isa nearly rectangular parallelepiped member having substantially the samelength as the head main body 1 a. The base block 75 made of a metallicmaterial such as stainless steel has a function as a light structure forreinforcing the holder 72. The holder 72 is made up of a holder mainbody 73 disposed near the head main body 1 a, and a pair of holdersupport portions 74 each extending on the opposite side of the holdermain body 73 to the head main body 1 a. Each holder support portion 74is as a flat member. The holder support portions 74 extend along thelength of the holder main body 73 and are disposed parallel to eachother at a predetermined interval.

[0045] A pair of skirt portions 73 a, each protruding downward, areprovided in both end portions of the holder main body 73 in a subscanning direction perpendicular to the main scanning direction. Eitherskirt portion 73 a is formed through the length of the holder main body73. As a result, in the lower portion of the holder main body 73, anearly rectangular parallelepiped groove 73 b is defined by the pair ofskirt portions 73 a. The base block 75 is received in the groove 73 b.The upper face of the base block 75 is bonded to the bottom of thegroove 73 b of the holder main body 73 with an adhesive or the like. Thethickness of the base block 75 is somewhat larger than the depth of thegroove 73 b of the holder main body 73. As a result, the lower end ofthe base block 75 protrudes downward beyond the skirt portions 73 a.

[0046] Within the base block 75, as passages for ink to be supplied tothe head main body 1 a, two ink reservoirs 3 are formed as two nearlyrectangular parallelepiped spaces, as hollow regions, extending alongthe length of the base block 75. These two ink reservoirs 3 areseparated by a partition 75 a extending along the length of the baseblock 75. As a result, the ink reservoirs 3 extend parallel to eachother along the length of the base block 75 at a predetermined interval.In FIG. 2, an opening 3 b (see FIG. 3) connecting to an ink reservoir 3is formed in the left portion of the lower face 75 b of the base block75 at a position corresponding to the ink reservoir 3. Each inkreservoir 3 is connected through a non-illustrated supply tube to anon-illustrated ink tank within the printer main body. Thus, the inkreservoir 3 is suitably supplied with ink from the ink tank.

[0047] In the lower face 75 b of the base block 75, the vicinity of eachopening 3 b protrudes downward from the surrounding portion. The headmain body 1 a supported under the base block 75 includes therein anactuator unit 21 and an ink passage unit 4 bonded to the lower face ofthe actuator unit 21. The base block 75 is joined with the ink passageunit 4 (see FIG. 2) of the head main body 1 a only in the vicinity 75 cof each opening 3 b of the lower face 75 b of the base block 75. Thus,the region of the lower face 75 b of the base block 75 other than thevicinity 75 c of each opening 3 b is distant from the head main body 1a, The actuator unit 21 is disposed within the distance.

[0048] A driver IC 80 is fixed to the outer side face of each holdersupport portion 74 of the holder 72, with an elastic member 83 such as asponge being interposed between them. A heat sink 82 is disposed inclose contact with the outer side face of the driver IC 80. The heatsink 82 is made of a nearly rectangular parallelepiped member forefficiently radiating heat generated in the driver IC 80. A flexibleprinted circuit (FPC) 50 as a power supply member, as will be describedlater in detail, is connected to the driver IC 80. The substrate 81 isdisposed outside the FPC 50 above the driver IC 80 and the heat sink 82.The upper face of the heat sink 82 is bonded to the substrate 81 with aseal member 84. Also, the lower face of the heat sink 82 is bonded tothe FPC 50 with a seal member 84. In order that a driving signal outputfrom the driver IC 80 can be transmitted to any individual electrode 35(see FIGS. 10A and 10B) formed on a surface of the actuator unit 21 aswill be described later in detail, the FPC 50 is electrically connectedto both of the driver IC 80 and the individual electrodes 35.

[0049] Between the lower face of each skirt portion 73 a of the holdermain body 73 and the upper face of the ink passage unit 4, a seal member85 is disposed to sandwich the FPC 50. Thus, the FPC 50 is fixed withthe seal member 85 to the ink passage unit 4 and the holder main body73. Therefore, even if the head main body 1 a is elongated, the headmain body 1 a can be prevented from being bent, the interconnectingportion between the FPC 50 and each individual electrode 35 (see FIGS.10A and 10B) formed on the surface of the actuator unit 21 can beprevented from receiving stress, and the FPC 50 can surely be held.

[0050] Referring to FIG. 1, in the vicinity of each lower corner of theinkjet head 1 along the main scanning direction, six protruding portions30 a are disposed at regular intervals along the corresponding side wallof the inkjet head 1. These protruding portions 30 a are provided atboth ends in the sub scanning direction of a nozzle plate 30 (see FIG.6) in the lowermost layer of the head main body 1 a. The nozzle plate 30is bent by about 90 degrees along the boundary line between eachprotruding portion 30 a and the other portion. The protruding portions30 a are provided at positions corresponding to the vicinities of bothends of various sizes of papers to be used for printing. Each bentportion of the nozzle plate 30 has a shape not right-angled but rounded.This makes it hard to bring about clogging of a paper, i.e., jamming,which may occur because the leading edge of the paper, which has beentransferred to approach the head 1, is stopped by the side face of thehead 1.

[0051] In FIG. 3, an ink reservoir 3 formed in the base block 75 isimaginarily illustrated with a broken line. As illustrated in FIG. 3,the head main body 1 a has a rectangular shape in plane extending in onedirection, i.e., main scanning direction. The head main body 1 aincludes therein an ink passage unit 4 in which a large number ofpressure chambers 10 and a large number of ink ejection ports 8 at thefront ends of nozzles (as for both, see FIGS. 5 an 6), as will bedescribed later. Trapezoidal actuator units 21 arranged in two rows in azigzag manner are bonded to the upper face of the ink passage unit 4.Each actuator unit 21 is disposed such that its parallel opposed sides,i.e., its upper and lower sides, extend along the length of the inkpassage unit 4. The oblique sides of each neighboring actuator units 21overlap each other in the width of the ink passage unit 4.

[0052] Each region in the lower face of the ink passage unit 4corresponding to the region where an actuator unit 4 is bonded is an inkejection region. In the surface of each ink ejection region; a largenumber of ink ejection ports 8 are arranged in a matrix, as will bedescribed later. Within the base block 75 disposed above the ink passageunit 4, the ink reservoirs 3 are formed along the length of the baseblock 75. Each ink reservoir 3 is connected to a non-illustrated inktank through the opening 3 a provided at one end of the ink reservoir 3,so that the ink reservoir 3 is always filled up with ink. In each inkreservoir 3, pairs of openings 3 b are provided in regions where noactuator unit 21 is present, so as to be arranged in a zigzag manneralong the length of the ink reservoir 3.

[0053]FIG. 4 is an enlarged view of a region enclosed with an alternatelong and short dash line in FIG. 3. As illustrated in FIGS. 3 and 4,each ink reservoir 3 is connected through an opening 3 b to a manifoldchannel 5 within the ink passage unit 4 disposed under the opening 3 b.Each opening 3 b is provided with a non-illustrated filter for catchingdust and dirt contained in ink. The front end portion of each manifoldchannel 5 branches into two sub manifold channels 5 a. In the lowerportion of one actuator unit 21, two sub manifold channels 5 a extendfrom each of the two openings 3 b on both sides of the actuator unit 21in the length of the inkjet head 1. That is, in the lower portion of oneactuator unit 21, four sub manifold channels 5 a in total extend alongthe length of the inkjet head 1. Each sub manifold channel 5 a is filledup with ink supplied from the corresponding ink reservoir 3.

[0054]FIG. 5 is an enlarged view of a region enclosed with an alternatelong and short dash line in FIG. 4. Either of FIGS. 4 and 5 is avertical view of a plane in which many pressure chambers 10 are arrangedin a matrix in the ink passage unit 4. Pressure chambers 10, apertures12, nozzles (ink ejection ports 8 formed at the respective tips of thenozzles are only illustrated in FIGS. 4 and 5), sub manifold channels 5a, etc., as components of the ink passage unit 4, are disposed atdifferent levels from one another perpendicularly to FIGS. 4 and 5 (seeFIG. 6).

[0055] In FIGS. 4 and 5, to make it easy to understand the figures, thepressure chambers 10, the apertures 12, etc., are illustrated with solidlines though they should be illustrated with broken lines because theyare within the actuator unit 21 or ink passage unit 4.

[0056] As illustrated in FIGS. 4 and 5, many ground electrodes 38 asperipheral electrodes each having a circular shape are provided near theouter edges of the upper face of each actuator unit 21. The groundelectrodes 38 are arranged substantially at regular intervals. Thus, theregion of the surface of the actuator unit 21 where individualelectrodes 35 (see FIGS. 10A and 10B) are formed is entirely surroundedby the ground electrodes 38.

[0057]FIG. 6 is a partial sectional view of the head main body 1 a ofFIG. 3 taken along line VI-VI in FIG. 5. As apparent from FIG. 6, eachink ejection port 8 is formed at the tip end of a tapered nozzle.Between a pressure chamber 10 and a sub manifold channel 5 a, anaperture 12 extends substantially parallel to the surface of the inkpassage unit 4, like the pressure chamber 10. The aperture 12 is forrestricting the ink flow to give the passage a suitable resistance,thereby intending the stabilization of ink ejection. Each ink ejectionport 8 is connected to a sub manifold channel 5 a through a pressurechamber 10 (length: 900 micrometer, width: 350 micrometer) and anaperture 12. Thus, within the inkjet head 1 formed are ink passages 32each extending from a non-illustrated ink tank to an ink ejection port 8through an ink reservoir 3, a manifold channel 5, a sub manifold channel5 a, an aperture 12, and a pressure chamber 10.

[0058] As apparent from FIG. 6, any aperture 12 is provided at a leveldifferent from that of the corresponding pressure chamber 10. Therefore,within a region of the ink passage unit 4 corresponding to the inejection region under each actuator unit 21, the aperture 12 and submanifold channel 5 a connected to one pressure chamber 10 can bedisposed to overlap in plane a pressure chamber 10 neighboring the aboveone pressure chamber 10. As a result, because pressure chambers 10 canbe densely arranged close to each other, image printing at a highresolution can be realized with an inkjet head 1 having a relativelysmall occupation area.

[0059] In the plane of FIGS. 4 and 5, pressure chambers 10 are arrangedwithin an ink ejection region in two directions, i.e., a direction alongthe length of the inkjet head 1 (first arrangement direction) and adirection somewhat oblique to the width of the inkjet head 1 (secondarrangement direction). The first and second arrangement directions forman angle theta somewhat smaller than the right angle. The ink ejectionports 8 are arranged at 50 dpi in the first arrangement direction. Onthe other hand, the pressure chambers 10 are arranged in the secondarrangement direction such that the ink ejection region corresponding toone actuator unit 21 includes twelve pressure chambers 10. The shift tothe first arrangement direction due to the arrangement in which twelvepressure chambers 10 are arranged in the second arrangement direction,corresponds to one pressure chamber 10. Therefore, within the wholewidth of the inkjet head 1, in a region of the interval between two inkejection ports 8 neighboring each other in the first arrangementdirection, there are twelve ink ejection ports 8. At both ends of eachink ejection region in the first arrangement direction, corresponding toan oblique side of the actuator unit 21, the above condition issatisfied by making a compensation relation to the ink ejection regioncorresponding to the opposite actuator unit 21 in the width of theinkjet head 1. Therefore, in the inkjet head 1 according to thisembodiment, by ejecting ink droplets in order through a large number ofink ejection ports 8 arranged in the first and second arrangementdirections with relative movement of a print paper along the width ofthe inkjet head 1, printing at 600 dpi in the main scanning directioncan be performed.

[0060] Next, the construction of the ink passage unit 4 will bedescribed in more detail with reference to FIG. 7. Referring to FIG. 8,pressure chambers 10 are arranged an rows in the first arrangementdirection at predetermined intervals at 500 dpi. Twelve rows of pressurechambers 10 are arranged in the second arrangement direction. As thewhole, the pressure chambers 10 are two-dimensionally arranged in theink ejection region corresponding to one actuator unit 21.

[0061] The pressure chambers 10 are classified into two kinds, i.e.,pressure chambers 10 a in each of which a nozzle is connected to theupper acute portion in FIG. 7, and pressure chambers 10 b in each ofwhich a nozzle is connected to the lower acute portion. Pressurechambers 10 a and 10 b are arranged in the first arrangement directionto form pressure chamber rows 11 a and 11 b, respectively. Asillustrated in FIG. 7, in the ink ejection region corresponding to oneactuator unit 21, from the lower side of FIG. 7, there are disposed twopressure chamber rows 11 a and two pressure chamber rows 11 bneighboring the upper side of the pressure chamber rows 11 a. The fourpressure chamber rows of the two pressure chamber rows 11 a and the twopressure chamber rows 11 b constitute a set of pressure chamber rows.Such a set of pressure chamber rows is repeatedly arranged three timesfrom the lower side in the ink ejection region corresponding to oneactuator unit 21. A straight line extending through the upper acuteportion of each pressure chamber in each of pressure chamber rows 11 aand 11 b crosses the lower oblique side of each pressure chamber in thepressure chamber row neighboring the upper side of that pressure chamberrow.

[0062] As described above, when viewing perpendicularly to FIG. 7, twofirst pressure chamber rows 11 a and two second pressure chamber rows 11b, in which nozzles connected to pressure chambers 10 are disposed atdifferent positions, are arranged alternately to neighbor each other.Consequently, as the whole, the pressure chambers 10 are arrangedregularly. On the other hand, nozzles are arranged in a concentratedmanner in a central region of each set of pressure chamber rowsconstituted by the above four pressure chamber rows. Therefore, in casethat each four pressure chamber rows constitute a set of pressurechamber rows and such a set of pressure chamber rows is repeatedlyarranged three times from the lower side as described above, there isformed a region where no nozzles exist, in the vicinity of the boundarybetween each neighboring sets of pressure chamber rows, i.e., on bothsides of each set of pressure chamber rows constituted by four pressurechamber rows. Wide sub manifold channels 5 a extend there for supplyingink to the corresponding pressure chambers 10. In this embodiment, inthe ink ejection region corresponding to one actuator unit 21, four widesub manifold channels 5 a in total are arranged in the first arrangementdirection, i.e., one on the lower side of FIG. 7, one between thelowermost set of pressure chamber rows and the second lowermost set ofpressure chamber rows, and two on both sides of the uppermost set ofpressure chamber rows.

[0063] As illustrated in FIG. 7, nozzles connected to ink ejection ports8 for ejecting ink are arranged in the first arrangement direction atregular intervals at 50 dpi to correspond to the respective pressurechambers 10 regularly arranged in the first arrangement direction. Onthe other hand, while twelve pressure chambers 10 are regularly arrangedalso in the second arrangement direction forming an angle theta with thefirst arrangement direction, twelve nozzles corresponding to the twelvepressure chambers 10 include ones each connected to the upper acuteportion of the corresponding pressure chamber 10 and ones each connectedto the lower acute portion of the corresponding pressure chamber 10, asa result, they are not regularly arranged in the second arrangementdirection at regular intervals.

[0064] If all nozzles are connected to the same-side acute portions ofthe respective pressure chambers 10, the nozzles are regularly arrangedalso in the second arrangement direction at regular intervals. In thiscase, nozzles are arranged so as to shift in the first arrangementdirection by a distance corresponding to 600 dpi as resolution uponprinting per pressure chamber row from the lower side to the upper sideof FIG. 7. Contrastingly in this embodiment, because four pressurechamber rows of two pressure chamber rows 11 a and two pressure chamberrows 11 b constitute a set of pressure chamber rows and such a set ofpressure chamber rows is repeatedly arranged three times from the lowerside, the shift of nozzle position in the first arrangement directionper pressure chamber row from the lower side to the upper side of FIG. 7is not always the same.

[0065] In the inkjet head 1 of this embodiment, a band region R will bediscussed that has a width of about 508.0 micrometer corresponding to 50dpi in the first arrangement direction and extends perpendicularly tothe first arrangement direction. In the band region R, any of twelvepressure chamber rows includes only one nozzle. That is, when such aband region R is defined at an arbitrary position in the ink ejectionregion corresponding to one actuator unit 21, twelve nozzles are alwaysdistributed in the band region R. The positions of points respectivelyobtained by projecting the twelve nozzles onto a straight line extendingin the first arrangement direction are distant from each other by adistance corresponding to 600 dpi as resolution upon printing.

[0066] When the twelve nozzles included in one band region R are denotedby (1) to (12) in order from one whose projected image onto a straightline extending in the first arrangement direction is the leftmost, thetwelve nozzles are arranged in the order of (1), (7), (2), (8), (5),(11), (6), (12), (9), (3), (10), and (4) from the lower side.

[0067] In the thus-constructed inkjet head 1 of this embodiment, byproperly driving active portions in the actuator unit 21, a character,an figure, or the like, having a resolution of 600 dpi can be formed.That is, by selectively driving active portions corresponding to thetwelve pressure chamber rows in order in accordance with the transfer ofa print medium, a specific character or figure can be printed on theprint medium.

[0068] By way of example, a case will be described wherein a straightline extending in the first arrangement direction is printed at aresolution of 600 dpi. First, a case will be briefly described whereinnozzles are connected to the same-side acute portions of pressurechambers 10. In this case, in accordance with transfer of a printmedium, ink ejection starts from a nozzle in the lowermost pressurechamber row in FIG. 7. Ink ejection is then shifted upward withselecting a nozzle belonging to the upper neighboring pressure chamberrow in order. Ink dots are thereby formed in order in the firstarrangement direction with neighboring each other at 600 dpi. Finally,all the ink dots form a straight line extending in the first arrangementdirection at a resolution of 600 dpi.

[0069] On the other hand, in this embodiment, ink ejection starts from anozzle in the lowermost pressure chamber row 11 a in FIG. 7, and inkejection is then shifted upward with selecting a nozzle connected to theupper neighboring pressure chamber row in order in accordance withtransfer of a print medium. In this embodiment, however, because thepositional shift of nozzles in the first arrangement direction perpressure chamber row from the lower side to the upper side is not alwaysthe same, ink dots formed in order in the first arrangement direction inaccordance with the transfer of the print medium are not arranged atregular intervals at 600 dpi.

[0070] More specifically, as shown in FIG. 7, in accordance with thetransfer of the print medium, ink is first ejected through a nozzle (1)connected to the lowermost pressure chamber row 11 a in FIG. 7 to form adot row on the print medium at intervals of about 508.0 micrometercorresponding to 50 dpi. After this, as the print medium is transferredand the straight line formation position has reached the position of anozzle (7) connected to the second lowermost pressure chamber row 11 a,ink is ejected through the nozzle (7). The second ink dot is therebyformed at a position shifted from the first formed dot position in thefirst arrangement direction by a distance of six times the interval ofabout 42.3 micrometer corresponding to 600 dpi (about 42.3 micrometermultiplied by six makes about 254.0 micrometer).

[0071] Next, as the print medium is further transferred and the straightline formation position has reached the position of a nozzle (2)connected to the third lowermost pressure chamber row 11 b, ink isejected through the nozzle (2). The third ink dot is thereby formed at aposition shifted from the first formed dot position in the firstarrangement direction by a distance of the interval of about 42.3micrometer corresponding to 600 dpi. As the print medium is furthertransferred and the straight line formation position has reached theposition of a nozzle (8) connected to the fourth lowermost pressurechamber row 11 b, ink is ejected through the nozzle (8). The fourth inkdot is thereby formed at a position shifted from the first formed dotposition in the first arrangement direction by a distance of seven timesthe interval of about 42.3 micrometer corresponding to 600 dpi (about42.3 micrometer multiplied by seven makes about 296.3 micrometer). Asthe print medium is further transferred and the straight line formationposition has reached the position of a nozzle (5) connected to the fifthlowermost pressure chamber row 11 a, ink is ejected through the nozzle(5). The fifth ink dot is thereby formed at a position shifted from thefirst formed dot position in the first arrangement direction by adistance of four times the interval of about 42.3 micrometercorresponding to 600 dpi (about 42.3 micrometer multiplied by four makesabout 169.3 micrometer).

[0072] Afterward, in the same manner, ink dots are formed with selectingnozzles connected to pressure chambers 10 in order from the lower sideto the upper side in FIG. 7. In this case, when the number of a nozzlein FIG. 7 is N, an ink dot is formed at a position shifted from thefirst formed dot position in the first arrangement direction by adistance corresponding to (magnification n=N−1) multiplied by (intervalcorresponding to 600 dpi). When the twelve nozzles have been finallyselected, the gap between the ink dots to be formed by the nozzles (1)in the lowermost pressure chamber rows 11 a in FIG. 7 at an interval ofabout 508.0 micrometer corresponding to 50 dpi is filled up with elevendots formed at intervals of about 42.3 micrometer corresponding to 600dpi. Therefore, as the whole, a straight line extending in the firstarrangement direction can be drawn at a resolution of 600 dpi.

[0073]FIG. 8 is a partial exploded view of the head main body 1 a ofFIG. 6 and the FPC 50 bonded to the head main body 1 a. As illustratedin FIG. 8, a principal portion on the bottom side of the inkjet head 1has a layered structure laminated with eleven sheets in total, i.e.,from the top, an FPC 50, an actuator unit 21, a cavity plate 22, a baseplate 23, an aperture plate 24, a supply plate 25, manifold plates 26,27, and 28, a cover plate 29, and a nozzle plate 30. Of them, nineplates 22 to 30 other than the FPC 50 and the actuator unit 21constitute an ink passage unit 4.

[0074] As will be described later in detail, the actuator unit 21 islaminated with four piezoelectric sheets and provided with electrodes sothat one layer of the piezoelectric sheets includes portions to beactive portions when an electric field is applied, and the remainingthree layers are inactive layers. The cavity plate 22 is made of metal,in which a large number of substantially rhombic openings are formedcorresponding to the respective pressure chambers 10. Portions exceptthe openings of the cavity plate 22 constitutes wall portions 22 adefining each of the pressure chambers 10. The base plate 23 is made ofmetal, in which a connecting hole between each pressure chamber 10 ofthe cavity plate 22 and the corresponding aperture 12, and a connectinghole between the pressure chamber 10 and the corresponding ink ejectionport 8 are formed. The aperture plate 24 is made of metal, in which, inaddition to apertures 12, connecting holes are formed for connectingeach pressure chamber 10 of the cavity plate 22 to the corresponding inkejection port 8. The supply plate 25 is made of metal, in whichconnecting holes between each aperture 12 and the corresponding submanifold channel 5 a and connecting holes for connecting each pressurechamber 10 of the cavity plate 22 to the corresponding ink ejection port8 are formed. Each of the manifold plates 26, 27, and 2S is made ofmetal, which defines an upper portion of each sub manifold channel 5 aand in which connecting holes are formed for connecting each pressurechamber 10 of the cavity plate 22 to the corresponding ink ejection port8. The cover plate 29 is made of metal, in which connecting holes areformed for connecting each pressure chamber 10 of the cavity plate 22 tothe corresponding ink ejection port 8. The nozzle plate 30 is made ofmetal, in which tapered ink ejection ports 8 each functioning as anozzle are formed for the respective pressure chambers 10 of the cavityplate 22.

[0075] The ink passage 32 of FIG. 6 first extends upward from the submanifold channel 5 a, then extends horizontally in the aperture 12, thenfurther extends upward, then again extends horizontally in the pressurechamber 10, then extends obliquely downward in a certain length to getapart from the aperture 12, and then extends vertically downward towardthe ink ejection port 8.

[0076]FIGS. 9A and 9B are plan and perspective views illustrating theshape of the space forming the ink passage of FIG. 6, respectively.FIGS. 9A and 9B illustrates therein a filter 13 provided at theinterface between an aperture 12 and a sub manifold channel 5 a. Thefilter 13 is for removing dust contained in ink.

[0077] Next, the construction of an actuator unit 21 will be describedwith reference to FIGS. 10A and 10B. FIG. 10A is a lateral enlargedsectional view of a region enclosed with an alternate long and shortdash line in FIG. 6. FIG. 10B is a plan view illustrating shapes of anindividual electrode formed on a surface of an actuator unit 21, and aland.

[0078] As illustrated in FIG. 10A, an actuator unit 21 includes thereinfour piezoelectric sheets 41, 42, 43, and 44 having the same thicknessof about 15 micrometer. The piezoelectric sheets 41 to 44 constitute apiezoelectric element and are made into a continuous layered flat plate(continuous flat layers) that is disposed so as to extend over manypressure chambers 10 formed within one ink ejection region in the inkjethead 1. Thereby, the mechanical rigidity of the piezoelectric sheets 41to 44 can be kept high. Because the piezoelectric sheets 41 to 44 aredisposed so as to extend over many pressure chambers 10 as thecontinuous flat layers, individual electrodes 35 can be arranged at ahigh density by using, e.g., a screen printing technique. Therefore,also pressure chambers 10 (see FIGS. 10A and 10B) formed at positionscorresponding to main electrode portion s 35 a of the individualelectrodes 35 as will be described later can be arranged at a highdensity. This makes it possible to print a high-resolution image.

[0079] In this embodiment, each of the piezoelectric sheets 41 to 44 ismade of a lead zirconate titanate (PZT)-base ceramic material havingferroelectricity.

[0080] As illustrated in FIG. 10A, about 1 micrometer-thick individualelectrodes 35, each having a shape in plane as illustrated in FIG. 10B,are formed on the upper face of the uppermost piezoelectric sheet 41 atpositions corresponding to the respective pressure chambers 10. An about2 micrometer-thick common electrode 34 is interposed between thepiezoelectric sheet 41 and the piezoelectric sheet 42 neighboringdownward the piezoelectric sheet 41. The common electrode 34 is made ofa single conductive sheet extending substantially in the whole region ofone actuator unit 21. Each of the electrodes 34 and 35 is made of ametallic material of, e.g., an Ag—Pd-base alloy.

[0081] No electrode is provided between the piezoelectric sheet 42 andthe piezoelectric sheet 43 neighboring downward the piezoelectric sheet42, between the piezoelectric sheet 43 and the piezoelectric sheet 44neighboring downward the piezoelectric sheet 43, and on the lower faceof the piezoelectric sheet 44.

[0082] In a modification, many common electrodes 34 each having a shapelarger than that of a pressure chamber 10 so that the projection imageof each common electrode projected along the thickness of the commonelectrode includes the pressure chamber, may be provided for eachpressure chamber 10. In another modification, many common electrodes 34each having a shape somewhat smaller than that of a pressure chamber 10so that the projection image of each common electrode projected alongthe thickness of the common electrode is included in the pressurechamber, may be provided for each pressure chamber 10. Thus, the commonelectrode 34 may not always be a single conductive sheet formed on thewhole of the face of a piezoelectric sheet. In the above modifications,however, all the common electrodes must be electrically connected to oneanother so that the portion corresponding to any pressure chamber 10 isat the same potential.

[0083] As illustrated in FIG. 10B, each individual electrode 35 has anearly rhombic shape having a length of 850 micrometer and a width of250 micrometer in plane, substantially similar to that of the pressurechamber 10 as illustrated in FIG. 5. The individual electrode 35includes therein a main electrode portion 35 a opposed to the pressurechamber 10, and a connecting portion 35 b extending from one acutecorner of the main electrode portion 35 a to be opposed to the wallportion 22 a and not to be opposed to the pressure chamber 10. Acircular land 36 having a diameter of about 160 micrometer is providedon the end of the connecting portion 35 b opposite to the main electrodeportion 35 a. The land 36 is made of, e.g., gold containing glass frit.The land 36 is electrically connected to the individual electrode 35.

[0084] As illustrated in FIGS. 10A and 5, when viewing along thethickness of the piezoelectric sheets 41 to 44, the projection image ofthe main electrode portion 35 a of each individual electrode 35 isincluded in the corresponding pressure chamber 10 but the projectionimage of the land 36 is not included in the pressure chamber 10. Both ofthe land 36 and the connecting portion 35 b of each individual electrode35 are opposed to the wall portion 22 a.

[0085] The common electrode 34 as illustrated in FIG. 10A iselectrically connected to a ground electrode 38 as illustrated in FIG. 5through a non-illustrated through-hole formed in the piezoelectric sheet41. Any ground electrode 38 is formed on the upper face of thepiezoelectric sheet 41. The FPC 50 includes therein not only conductivepatterns 53 as will be described later (see FIGS. 11A to 11C) but alsonon-illustrated conductive patterns as wires for grounding. Whennon-illustrated ground terminals provided in the latter conductivepatterns are connected to the respective ground electrodes 38, thecommon electrode 34 connected to the ground electrodes 38 is kept at theground potential in the region corresponding to all pressure chambers10.

[0086] Next, drive of the actuator unit 21 of this embodiment will bedescribed. The piezoelectric sheets 41 to 44 of the actuator unit 21have been polarized in their thickness. Therefore, an individualelectrode 35 is set at a potential different from that of the commonelectrode 34 to apply an electric field to the piezoelectric sheet 41 inthe polarization, the portion of the piezoelectric sheet 41 to which theelectric field has bee applied works as an active portion and theportion is ready to expand or contract in thickness, i.e., in layers,and to contract or expand perpendicularly to the thickness, i.e., in aplane, by the transversal piezoelectric effect. On the other hand,because the remaining three piezoelectric sheets 42 to 44 are inactivelayers having no regions sandwiched by the individual electrode 35 andthe common electrode 34, they can not be deformed in their selves. Thatis, the actuator unit 21 has a so-called unimorph type structure inwhich the upper, i.e., distant from the pressure chamber 10, onepiezoelectric sheet 41 is a layer including active portions and thelower, i.e., near the pressure chamber 10, three piezoelectric sheets 42to 44 are inactive layers.

[0087] Therefore, when the driver IC 80 is controlled so that anelectric field is produced in the same direction as the polarization andan individual electrode 35 is set at a positive or negativepredetermined potential relative to the common electrode 34, the activeportion in the piezoelectric sheet 41 sandwiched by the individual andcommon electrodes 35 and 34 contracts in a plane, while thepiezoelectric sheets 42 to 44 do not contract in their selves. At thistime, as illustrated in FIG. 10A, the lowermost face of thepiezoelectric sheets 41 to 44 is fixed to the upper face of partitionspartitioning pressure chambers 10 formed in the cavity plate 22, as aresult, the piezoelectric sheets 41 to 44 are deformed into a convexshape toward the corresponding pressure chamber 10 by contracting in aplane by the transversal piezoelectric effect, which is called unimorphdeformation. Therefore, the volume of the pressure chamber 10 isdecreased to raise the pressure of ink. The ink is thereby ejectedthrough the corresponding ink ejection port 8. Afterward, when theindividual electrode 35 is returned to the original potential, thepiezoelectric sheets 41 to 44 return to the original flat shape and thepressure chamber 10 also returns to its original volume. Thus, thepressure chamber 10 sucks ink therein through the corresponding manifoldchannel 5.

[0088] In another driving method, all the individual electrodes 35 areset in advance at a different potential from that of the commonelectrode 34 so that the piezoelectric sheets 41 to 44 are deformed intoconvex shapes toward the respective pressure chambers 10. When anejecting request is issued, the corresponding individual electrode 35 isonce set at the same potential as that of the common electrode 34.Afterward, at a predetermined timing, the individual electrode 35 isagain set at the different potential from that of the common electrode34. In this case, at the timing when the individual electrode 35 is setat the same potential as that of the common electrode 34, thepiezoelectric sheets 41 to 44 return to their original shapes. Thecorresponding pressure chamber 10 is thereby increased in volume fromits initial state, i.e., the state that the potentials of bothelectrodes differ from each other, to suck ink from the correspondingmanifold channel 5 into the pressure chamber 10. Afterward, at thetiming when the individual electrode 35 is again set at the differentpotential from that of the common electrode 34, the piezoelectric sheets41 to 44 are deformed into a convex shape toward the pressure chamber10. The volume of the pressure chamber 10 is thereby decreased and thepressure of ink in the pressure chamber.10 increases to eject ink.

[0089] In case that the polarization occurs in the reverse direction tothe electric field applied to the piezoelectric sheet 41, the activeportion in the piezoelectric sheet 41 sandwiched by the individual andcommon electrodes 35 and 34 is ready to elongate perpendicularly to thepolarization. As a result, the piezoelectric sheets 41 to 44 aredeformed into a concave shape toward the pressure chamber 10 by thetransversal piezoelectric effect. Therefore, the volume of the pressurechamber 10 is increased to suck ink from the manifold channel 5.Afterward, when the individual electrode 35 return to their originalpotential, the piezoelectric sheets 41 to 44 also return to theiroriginal flat shape. The pressure chamber 10 thereby returns to itsoriginal volume to eject ink through the ink ejection port 6.

[0090] As illustrated in FIG. 11A, the FPC 50 includes therein a basefilm 51, conductive patterns 53 formed on the lower face of the basefilm 51, and a cover film 52 covering substantially the whole of thelower face of the base film 51. The base film 51 has a thickness ofabout 25 micrometer. Each conductive pattern 53 has a thickness of about9 micrometer. The cover film 52 has a thickness of about 20 micrometer.Through-holes 52 a each having an area smaller than that of a conductivepattern 53 are formed in the cover film 52 so as to correspond to therespective conductive patterns 53. The base film 51, the conductivepatterns 53, and the cover film 52 are put in layers with beingpositioned to one another so that the center of each through-hole 52 acorresponds to the center of a conductive pattern 53 and the peripheraledge of each conductive pattern 53 is covered with the cover film 52. Aterminal 54 of the FPC 50 is connected to the corresponding conductivepattern 53 through the through-hole 52 a.

[0091] Either of the base film 51 and the cover film 52 is made of aninsulating sheet material. In this embodiment, the base film 51 is madeof a polyimide resin. The cover film 52 is made of a photosensitivematerial. Because the cover film 52 is made of such a photosensitivematerial, a large number of through-holes 52 a can be easily formed.

[0092] Each conductive pattern 53 is made of a copper foil. Theconductive patterns 53 are wires connected to the driver IC 80 and madeinto a predetermined pattern on the lower face of the base film 51.

[0093] Each terminal 54 is made of a conductive material such as nickel.The terminal 54 plugs the corresponding through-hole 52 a and covers thelower face of the cover film 52 at the peripheral edge around thethrough-hole 52 a. The terminal 54 protrudes toward the piezoelectricsheet 41. The terminal 54 has a diameter of about 50 micrometer and athickness of about 30 micrometer from the lower face of the cover film52.

[0094] The FPC 50 includes therein a large number of terminals 54, eachof which corresponds to one land 36 (see FIGS. 10A and 10B). Therefore,each individual electrode 35 electrically connected to the correspondingland 36 is electrically connected to the driver IC 80 through anindependent conductive pattern 53 in the FPC 50. Thus, the potential ofeach pressure chamber 10 can be controlled independently.

[0095] Next, an example of method for fabricating a head main body 1 aof the inkjet head 1 will be described. To fabricate a head main body 1a, in general, an ink passage unit 4 and an actuator unit 21 areseparately fabricated in parallel and then they are bonded to eachother.

[0096] To fabricate an ink passage unit 4, each of plates 22 to 30 toconstitute the ink passage unit 4 is etched using a patternedphotoresist as a mask to form openings and recesses as illustrated inFIGS. 6 and 8 in the plates 22 to 30. Afterward, the nine plates 22 to30 are put in layers with an adhesive being interposed so that an inkpassage 32 as illustrated in FIG. 6 is formed therein. The plates 22 to30 is thus bonded to each other to form an ink passage unit 4.

[0097] To fabricate an actuator unit 21, first, a conductive paste to bea common electrode 34 is printed into a pattern on a green sheet of aceramic material to be a piezoelectric sheet 42. Afterward, fourpiezoelectric sheets 41 to 44 are put in layers with being positioned toeach other using a jig. The thus-obtained layered structure is baked ata predetermined temperature. The baked layered structure having noindividual electrode 35 is then bonded to the ink passage unit 4 with anadhesive such that the piezoelectric sheet 44 is in contact with thecavity plate 22.

[0098] Afterward, a conductive paste to be individual electrodes 35 isprinted into a pattern on a surface of the piezoelectric sheet 41.Further, a conductive paste to be lands 36 is printed into a pattern onone end of the conductive paste to be each individual electrode 35, morespecifically, on one end of the connecting portion 35 b of eachindividual electrode 35 (see FIGS. 10A and 10B). Afterward, through abaking process, the pastes are sintered. Thereby, individual electrodes35 are formed on the surface of the piezoelectric sheet 41 and further aland 36 is formed on one end of the connecting portion 35 b of eachindividual electrode 35.

[0099] Afterward, for supplying electric signals to the individualelectrodes 35, terminals of an FPC 50 are connected to the respectivelands 36. Further, through a predetermined process, manufacture of aninkjet head 1 is completed.

[0100] Next, a process for connecting a terminal to a land in amanufacturing method of an inkjet head according to the first embodimentof the present invention will be described with reference to FIGS. 11Ato 11D. FIGS. 11A to 11C illustrate a process for connecting a terminalto a land, in the order of steps. FIG. 11D is a plan view, correspondingto FIG. 10B, illustrating an occupation area of an epoxy resin in thestate of FIG. 11C.

[0101] First, as illustrated in FIG. 11A, a solder 60 having a thicknessof about 7 to 8 micrometer is disposed so as to cover the whole of asurface of the terminal 54. Afterward, the FPC 50 including theterminals 54 is opposed to an epoxy resin 62 applied to a surface of aflat member 64, and then each terminal 54 is pressed onto the flatmember 64 so that the epoxy resin 62 is transferred thereto. Thereby, asillustrated in FIG. 11B, the epoxy resin 62 having a diameter of about0.1 mm adheres to the surface of the solder 60. The epoxy resin 62 inFIG. 11A preferably has a thickness of 10 micrometer, and about 60 to70% the thickness of the epoxy resin 62 is transferred to the surface ofthe solder 60 though it depends on wettability.

[0102] Afterward, with positioning each terminal 54 to the correspondingland 36, the FPC 50 is brought near the piezoelectric sheet 41 and thenpressed in a direction so that the land 36 and the terminal 54 get closeto each other. In this pressing process, first, the epoxy resin 62 comesinto contact with the surface of the land 36. In progress of thepressing process, the epoxy resin 62 moves perpendicularly to adirection in which the land 36 and the terminal 54 are opposed to eachother, i.e., horizontally in FIG. 11B, and then the epoxy resin 62 isdischarged from the gap between the land 36 and the terminal 54.Thereby, the epoxy resin 62 spreads out onto the connecting portion 35 bof the surface electrode 35 and surrounds the land 36, the terminal 54,and the solder 60, as illustrated in FIGS. 11C and 11D. The epoxy resin62 connects the cover film 52 of the FPC 50 to the piezoelectric sheet41. Accordingly, the solder 60 is disposed in the gap between the land36 and the terminal 54, while the epoxy resin 62 is disposed in a regionaround the land 36 and the terminal 54 with connecting both to eachother. That is, only the solder 60 is interposed between the land 36 andthe terminal 54 so that the land 36 and the terminal 54 come intocontact so as to be electrically connected to each other through thesolder 60.

[0103] Afterward, for example, a non-illustrated ceramic heater isdisposed on the surface of the base film 51 of the FPC 50 to heat. Atthis time, the epoxy resin 62 is thermosetting in which the heated resinis softened to a degree that it can be processed, the further heatedresin is hardened by a chemical reaction, and the once-hardened resin isnever softened even when it is heated. When the solder 60 starts to bemelted by being heated, the epoxy resin 62 is scarcely hardened and in asoft condition. The epoxy resin 62 is scarcely deformed with heat andkept substantially in the condition as illustrated in FIGS. 11C and 11D.Afterward, by being further heated, the epoxy resin 62 becomes insubstantially the same state as in FIGS. 11C and 11D, because the epoxyresin 62 has the viscosity as well. That is, the epoxy resin 62 becomescompletely hardened, in the state when the above-described pressingprocess is completed, with connecting both the cover film 52 and thepiezoelectric sheet 41 and also with covering the peripheries of solder60 connecting the land 36 and the terminal 54.

[0104] The epoxy resin 62 and the solder 60 are not mixed with eachother in the heating process.

[0105]FIG. 12B illustrates a modification of the process for connectinga terminal to a land in the manufacturing method of the inkjet headaccording to the above-described embodiment. FIG. 12 is a partialsectional view corresponding to FIG. 11B. In the above-describedembodiment, as illustrated in FIG. 11B, the epoxy resin 62 adheres tothe surface of the solder 60. In this modification, however, the epoxyresin 62 adheres not to the surface of the solder 60 but to the surfaceof the land 36. Even in case of performing the pressing and heatingprocesses in the state of FIG. 12, the same state as in FIGS. 11C and11D of the above-described embodiment is obtained as a result.

[0106] As described above, in the inkjet head 1 of this embodiment,because the interconnecting portion between each land 36 and thecorresponding terminal 54 is in a region not opposed to thecorresponding pressure chamber 10, hindrance of deformation of thepiezoelectric element of the actuator unit 21, i.e., the piezoelectricsheets 41 to 44, can be suppressed. Therefore, because the volume ofeach pressure chamber 10 can be efficiently reduced, the problem ofdeterioration of ink ejection performance is relieved.

[0107] Further, because the solder 60 is covered with the epoxy resin 62that has fluidity lower than that of a metallic material such as thesolder 60 even by being heated, movement of the solder 60 can besuppressed. In addition, because the epoxy resin 62 has spread out tothe outside of the connecting portion 35 b of the surface electrode 35and surrounds the land 36, the terminal 54, and the solder 60 (see FIGS.11C and 11D), such problems are relieved as hindrance of deformation ofthe piezoelectric element, rise of the resistance, and braking, whichmay occur when the solder 60 adheres to the main electrode portion 35 aof the individual electrodes 35, and also a short circuit betweenterminals which may occur when the solder 60 adheres to the neighboringterminal interconnecting portions.

[0108] In case of using only solder, from the viewpoint of bondingstrength, it is required to relatively increase the area of theinterconnecting portion between a terminal and an electrode, or toincrease the amount of use of solder. However, either of the measures ofincreasing the interconnecting portion between a terminal and anelectrode and of increasing the amount of use of solder isdisadvantageous for a highly dense arrangement of pressure chambers.Such a highly dense arrangement of pressure chambers is a recent demandfor inkjet heads, and therefore there is a tendency that theinterconnecting portions between electrodes provided to correspond tothe respective pressure chambers and terminals of a printed circuitboard are arranged at narrow intervals. In case of such a narrowinterval between interconnecting portions, it is difficult to increasethe area of each interconnecting portion. On the other hand, in case ofincreasing the amount of use of solder, the problems such as hindranceof deformation of the piezoelectric element, rise of the resistance,braking, and a short circuit may become more remarkable.

[0109] In this embodiment, however, because the epoxy resin 62 surroundsthe land 36, the terminal 54, and the solder 60, sufficient bondingstrength can be ensured even if the bonding area between the land 36 andthe terminal 54 is made relatively small or the amount of use of solder60 is made relatively little. That is, this embodiment suitably meetsthe recent demand of a highly dense arrangement of pressure chambers,i.e., even in case that the pressure chambers 10 are arranged in amatrix in a plane of the ink passage unit 4 as in this embodiment sothat the pressure chambers 10 are highly densely arranged.

[0110] Because the epoxy resin 62 is disposed in a region opposed to nopressure chamber 10, hindrance of deformation of the piezoelectricelement of the actuator unit 21, i.e., the piezoelectric sheets 41 to44, can be suppressed more surely.

[0111] As illustrated in FIGS. 11C and 11D, the epoxy resin 62 isdisposed only in the vicinity of the land 36 and does not adhere to thepiezoelectric sheet 41 and the individual electrode 35 more than it isneeded. This is suitable from the viewpoint of suppressing hindrance ofdeformation of the piezoelectric element of the actuator unit 21, i.e.,the piezoelectric sheets 41 to 44, and the economical viewpoint ofsuppressing the amount of use of the material.

[0112] Because the thermosetting epoxy resin 62 is used, the epoxy resin62 can be hardened with heat in a state that the epoxy resin 62 coversthe whole of the outer surface of the solder 60. That is, when thesolder 60 is melted by being heated to have high fluidity, the epoxyresin 62 is in a soft state to suppress the flow of the solder 60. Theepoxy resin 62 is then hardened. This surely suppresses the movement ofthe solder 60 from the vicinity of the land 36, and further improves thebonding strength between the terminal and electrode.

[0113] In general, in case of using only solder, flux must be used. Incase of using the epoxy resin 62 as in this embodiment, however, becausethe epoxy resin 62 tends to contain a small amount of ingredientfunctioning similarly to the flux, no flux need be used. This isconvenience economically and environmentally.

[0114] Because pressure chambers 10 are arranged in a matrix in a planeof the ink passage unit 4, a large number of nozzles can be provided ata high density and therefore image printing at a high resolution ispossible.

[0115] In FIGS. 11A to 11C and 12, either of the surfaces of theterminal 54 and the land 36 is smooth. In practice, however, for reasonsof process, at least minute unevenness in height is generally formed ineither of the surfaces of the terminal 54 and the land 36. Therefore, itis difficult to bring a large number of terminals 54 of the FPC 54 and alarge number of lands 36 of the actuator unit 21 into sure contact witheach other by pressing evenly the FPC 50 and the actuator unit 21 ontoeach other so that the FPC 50 and the actuator unit 21 is brought neareach other. For this reason, in this embodiment, the solder 60 isinterposed in the narrow gap between the terminal 54 and the land 36 ineach pair so that electrical connection between them is sure.

[0116] In the manufacturing method of this embodiment, because theinterconnecting portion between the terminal 54 and the land 36 is in aregion opposed to no pressure chamber 10, the force for pressing theterminal 54 onto the land 36 can be effectively transmitted incomparison with a case wherein the interconnecting portion is in aregion opposed to a pressure chamber 10. This makes it easy to connectthe terminal 54 and the land 36 to each other.

[0117] In the manufacturing method of this embodiment, the pressingprocess is performed after the solder 60 and the epoxy resin 62 aredisposed between the terminal 54 and the land 36 in the order of thesolder 60 and the epoxy resin 62 from the upper side. Thereby, beforethe heating process, the state as illustrated in FIGS. 11C and 11D canbe easily realized wherein the epoxy resin 62 has been discharged fromthe gap between the terminal 54 and the land 36 and covers the outersurface of the solder 60.

[0118] Next, a modification of the inkjet head according to the firstembodiment of the present invention will be described with reference toFIGS. 13A to 13C. FIGS. 13A and 13B illustrate a process for connectinga terminal to a land, in the order of steps. FIG. 13C is a plan view,corresponding to FIG. 10B, illustrating an occupation area of an epoxyresin in the state of FIG. 13B. This modification is the same as theabove-described embodiment except the shape of the epoxy resin 62 andthus description of the same feature will be omitted.

[0119] In this modification, as illustrated in FIG. 13A, the epoxy resin62 is disposed only in a region between the land 36 and thecorresponding pressure chamber 10 (see FIG. 10A) before the terminal 54is pressed onto the land 36. In this modification, the state after thesame pressing process as that described above is performed is asillustrated in FIGS. 13B and 13C. That is, the epoxy resin 62 coversonly part of the solder 60, more specifically, only a portion of thesolder 60 between the land 36 and the pressure chamber 10 (see FIG.10A).

[0120] In this modification, the force necessary for spreading the epoxyresin 62 out may be weak in comparison with that in the above-describedembodiment. Therefore, the terminal 54 can be connected to the land 36by a relatively weak pressing force. This makes the connecting workeasy.

[0121] If an excessive pressing force is applied to the piezoelectricsheets 41 to 44 constituting the actuator unit 21, it may hinder the inkejection performance. However, this modification can relieve thatproblem.

[0122] Further, because the epoxy resin 62 can suppress movement of themelted solder 60 to the main electrode portion 35 a of the individualelectrode 35, the problems such as hindrance of deformation of thepiezoelectric element, rise of the resistance, and braking are relieved.From the viewpoint of relieving the problem of a short circuit inaddition to the problem described above, however, it is preferable thatthe epoxy resin 62 spreads out to the outside of the connecting portion35 b to surround the land 36, the terminal 54, and the solder 60 as inthe above-described embodiment.

[0123] The epoxy resin 62 may cover at least part of the solder 60, Theportion of the solder 60 to be covered with the epoxy resin 62 can beadequately modified. For example, when the epoxy resin 62 is disposedonly in a region between neighboring connecting portions between landand terminal, a short circuit between the terminals can be suppressed,though the effect of preventing the hindrance of deformation of thepiezoelectric element, rise of the resistance, and braking can not beobtained.

[0124] Further, the position where the solder 60 is disposed before thepressing process, is not limited to the whole of the surface of theterminal 54 as illustrated in FIG. 11A. It may be part of the surface ofthe terminal 54. Furthermore, it is not limited to the surface of theterminal 54. It may be the surface of the land 36. In this case, theepoxy resin 62 is disposed on the solder 60, i.e., on the side near theterminal 54.

[0125] As illustrated in FIG. 11C or 13B, the solder 60 is disposed inthe gap between the land 36 and the terminal 54 and in the regionbridging the gap along the peripheries of the land 36 and the terminal54. However, the present invention is not limited to this feature. Forexample, even when the solder 60 is disposed only in the gap between theland 36 and the terminal 54, electrical connection between them can berealized. Further, if all the terminals 54 can be surely brought intocontact with the respective lands 36 in the pressing process, the solder60 may be disposed only in the region bridging the gap between each pairof land 36 and terminal 54 along the peripheries of the land 36 and theterminal 54. Even in this case, electrical connection between the lands36 and the terminals 54 can be realized.

[0126] Further, as long as the solder 60 can be prevented from spreadingout, the epoxy resin 62 may not be in contact with the cover sheet 52,and may not surround the land 36, the terminal 54, and the solder 60.However, when the epoxy resin 62 is in contact with the cover sheet 52,improvement of bonding between the land 36 and the terminal 54 isachieved in addition to the advantage of suppressing problems due tomovement of the solder 60 as described above.

[0127] Further, the epoxy resin 62 may be disposed in a region opposedto the pressure chamber 10. From the viewpoint of suppressing hindranceof deformation of the piezoelectric element of the actuator unit 21,i.e., the piezoelectric sheets 41 to 44, however, the epoxy resin 62 ispreferably disposed in a region which does not contribute to thedeformation of the piezoelectric sheets 41 to 44, even the regionopposed to the pressure chamber 10, or in a region not opposed to thepressure chamber 10 as in the above-described embodiment.

[0128] The epoxy resin 62 is disposed only in the vicinity of each land36. However, the present invention is not limited to this feature. Forexample, the epoxy resin 62 can be disposed at an arbitrary position ina region between the FPC 50 and the piezoelectric sheet 41. From theviewpoint of suppressing hindrance of deformation of the piezoelectricelement of the actuator unit 21, i.e., the piezoelectric sheets 41 to44, and from the economical viewpoint of suppressing the amount of useof the material, however, the epoxy resin 62 is desirably disposed onlyin the vicinity of each land 36.

[0129] Further, in place of the epoxy resin 62, another thermosettingresin can be used.

[0130] Further, the metallic bond for electrically connecting theterminal 54 to the land 36 is not limited to the solder 60. Variousmetallic bonds such as tin are usable. However, the thermosetting resinand metallic bond to be used in the present invention must have naturesin which both are not mixed with each other upon being heated.

[0131] Next, another modification of the inkjet head according to thefirst embodiment of the present invention will be described withreference to FIGS. 14A to 14C. FIGS. 14A and 14B illustrate a processfor connecting a terminal to a land, in the order of steps. FIG. 14C isa plan view, corresponding to FIG. 10B, illustrating an occupation areaof an epoxy resin in the state of FIG. 14B. This modification is thesame as the above-described embodiment except using a protrusion 162 inplace of the epoxy resin 62 and thus description of the same featurewill be omitted.

[0132] In this modification, as illustrated in FIG. 14A, a protrusion162 has been formed on the connecting portion 35 b of each individualelectrode 35 in advance before the terminal 54 is pressed onto the land36. As illustrated in FIG. 14C, the protrusion 162 extends to theoutside of the connecting portion 35 b substantially perpendicularly toa line extending through the main electrode portion 35 a of theindividual electrode 35 and the land 36. The protrusion 162 may be madeof a thermosetting resin such as an epoxy resin, or may be made of amaterial other than thermosetting resins. In Addition, the protrusion162 may be made of an inorganic material such as a silicon oxide andsilicon nitride. That is, various materials can be used to form theprotrusion 162 as long as the material has lower wettability (affinity)to the solder 60 having melted, if not intending the connection betweenthe cover film 52 and the piezoelectric sheet by the protrusion 162.

[0133] After the protrusion 162 is formed on the connecting portion 35 bas illustrated in FIG. 14A, the ink passage unit 4 and the actuator unit21 are bonded to each other such that the land 36 and the protrusion 162are in a region not opposed to the corresponding pressure chamber 10.Afterward, the solder 60 is disposed on the surface of the terminal 54as described above, and then the pressing process is performed.

[0134] As apparent from FIGS. 14A and 14B, the protrusion 162 is notdeformed in the pressing process.

[0135] As shown in 14B, the protrusion 162 is in contact with the coversheet 52 of the FPC 50, and connects the actuator unit 21 and the FPC50. This connection of the actuator unit 21 and the FPC 50 by theprotrusion 162 strengthens bonding force between them. However, theprotrusion 162 may not connect the actuator unit 21 and the FPC 50, butneeds to suppress movement of the solder 60 having melted in solderingtoward the main electrode portion 35 a. For example, height of theprotrusion 162 may be smaller then the distance between the cover film52 and the piezoelectric sheet 41 formed by contact of the terminal 54and the land 36.

[0136] In this modification, the protrusion 162 suppresses movement ofthe solder 60 to the main electrode portion 35 a of the individualelectrode 35. Therefore, like the above-described embodiment, the effectis obtained of relieving the problems such as hindrance of deformationof a piezoelectric element, rise of the resistance, and braking.

[0137] Because the protrusion 162 extends across the connecting portion35 b to the outside of the connecting portion 35 b substantiallyperpendicularly to a line extending through the main electrode portion35 a and the land 36, movement of the solder 60 toward the mainelectrode portion 35 a of the individual electrode 35 can be effectivelysuppressed.

[0138] By adequately changing the height or position of the protrusion162, the effect of suppressing the movement of the solder 60 can becontrolled. For example, the protrusion 162 may be formed so as tosurround the land 36, the terminal 54, and the solder 60 like the epoxyresin 62 of the first embodiment.

[0139] Next, a process for connecting a terminal to a land in amanufacturing method of an inkjet head according to a second embodimentof the present invention will be described with reference to FIGS. 15Aand 15B. FIGS. 15A and 15B illustrate a process for connecting aterminal to a land, in the order of steps. This embodiment is the sameas the above-described first embodiment except the connecting portionbetween a terminal 54 and a land 36 and thus description of the samefeature will be omitted.

[0140] In this embodiment, an ACP (Anisotropic Conductive Paste) 63 isused for connecting a terminal 54 to a land 36, in place of using thesolder 60 and the epoxy resin 62.

[0141] First, as illustrated in FIG. 15A, an ACP 63 is disposed on asurface of a land 36 by, e.g., transferring or printing. Afterward, withpositioning each terminal 54 to the corresponding land 36, the FPC 50 isbrought near the piezoelectric sheet 41 and then pressed in a directionso that the land 36 and the terminal 54 get close to each other. In thispressing process, first, the ACP 63 comes into contact with the surfaceof the land 36. In progress of the pressing process, the most part ofthe ACP 63 moves perpendicularly to a direction in which the land 36 andthe terminal 54 are opposed to each other, i.e., horizontally in FIG.11B. Thereby, as illustrated in FIG. 15B, in the vicinity of the land36, the most part of the ACP 63 covers the side face of the terminal 54and surrounds the peripheries of the land 36 and the terminal 54. On theother hand, the remaining part of the ACP 63 stays in the narrow gapbetween the land 36 and the terminal 54, and conductive particles in theACP 63 electrically connects the land 36 and the terminal 54 to eachother.

[0142] Afterward, by performing the same heating process as in theabove-described first embodiment, the thermosetting ACP 63 is completelyhardened in substantially the same state as in FIG. 15B, i.e., in thestate when the above-described pressing process is completed.

[0143] As described above, in this embodiment, electrical connectionbetween the land 36 and the terminal 54 is realized by the ACP 63. Thus,without using the solder 60 as in the first embodiment, the terminal 54and the land 36 can be connected to each other only with a single bondof the ACP 63. This makes the manufacture relatively easy.

[0144] Also in this embodiment, like the first embodiment, because theinterconnecting portion between each land 36 and the correspondingterminal 54 is in a region not opposed to the corresponding pressurechamber 10, hindrance of deformation of the piezoelectric sheets 41 to44 can be suppressed. Therefore, because the volume of each pressurechamber 10 can be efficiently reduced, the problem of deterioration ofink ejection performance is relieved.

[0145] Further, because the ACP 63 is used for electrically connectingeach land 36 to the corresponding terminal 54 in place of a metallicbond such as solder 60, the problems such as hindrance of deformation ofa piezoelectric element, rise of the resistance, and braking, togetherwith the problem of a short circuit between terminals can be relieved.

[0146] Further, because the ACP 63 is disposed in a region not opposedto the pressure chamber 10, hindrance of deformation of thepiezoelectric element of the actuator unit 21, i.e., the piezoelectricsheets 41 to 44, can be suppressed.

[0147] Further, as apparent from FIG. 15B, because the ACP 63 surroundsthe land 36 and the terminal 54, sufficient bonding strength can beensured. Therefore, like the first embodiment, this embodiment alsosuitably meets the recent demand of a highly dense arrangement ofpressure chambers, i.e., even in case that the pressure chambers 10 arearranged in a matrix in a plane of the ink passage unit 4 as in thisembodiment so that the pressure chambers 10 are highly densely arranged.

[0148] Further, because the ACP 63 containing conductive particles isused, even in case that terminals 54 do not surely come into contactwith the respective lands 36 when the FPC 50 is brought near thepiezoelectric sheet 41, the ACP 63 is between each terminal 54 and thecorresponding land 36 to realize electrical connection between them.Besides, although solder 60 must be heated to about 200 degrees C. formelting, heating to about 100 degrees C. suffices in this embodiment.This is because the ACP 63 is hardened at about 100 degrees C.

[0149] The ACP 63 is disposed in the gap between the land 36 and theterminal 54 and in the region bridging the gap along the peripheries ofthe land 36 and the terminal 54. However, the present invention is notlimited to this feature. For example, even when the ACP 63 is disposedonly in the gap between the land 36 and the terminal 54, electricalconnection between them can be realized. Further, if all the terminals54 can be surely brought into contact with the respective lands 36 inthe pressing process, the ACP 63 may be disposed only in the regionbridging the gap between each pair of land 36 and terminal 54 along theperipheries of the land 36 and the terminal 54. Even in this case,electrical connection between the lands 36 and the terminals 54 can berealized.

[0150] The ACP 63 may not surround the land 36 and the terminal 54 andmay cover only part of the gap between them. Further, the presentinvention is not limited to the feature that the ACP 63 is disposed onlyin the vicinity of each land 36. For example, the ACP 63 can be disposedat an arbitrary position in a region between the FPC 50 and thepiezoelectric sheet 41 if the position is in a region not opposed to anypressure chamber 10. From the viewpoint of suppressing hindrance ofdeformation of the piezoelectric element of the actuator unit 21, i.e.,the piezoelectric sheets 41 to 44, and from the economical viewpoint ofsuppressing the amount of use of the material, however, the ACP 63 isdesirably disposed only in the vicinity of each land 36.

[0151] In this embodiment, the ACP 63 is used as a bond. However, thepresent invention is not limited to this feature. For example, variousother thermosetting resins such as an NCP (Non-conductive Paste) areusable. In case of using a thermosetting resin, e.g., an NCP, other thanthat containing conductive particles, such as the ACP 63, however, nogap must be formed between any terminal 54 and the corresponding land 36to bring them into contact with each other, and the resin must bedisposed around them. In case of including many terminals 54 and manylands 36 as in this embodiment, it is very difficult in practice toeliminate a gap from any connecting portion between them. For thisreason, each terminal 54 is preferably made of a relatively softmaterial such as gold. This makes it easy to eliminate a gap from anyconnecting portion.

[0152] Further, the position where the ACP 63 is disposed before thepressing process is not limited to the whole of the surface of each land36 as illustrated in FIG. 15A. It may be part of the surface of the land36 or may be a surface of each terminal 54.

[0153] Further, the pressure chambers 10 formed in the ink passage unit4 may not be arranged in a matrix. Further, the piezoelectric element ofthe actuator unit 21 may not have its size extending over pressurechambers 10 as the piezoelectric sheets 41 to 44. A piezoelectricelement may be provided for each pressure chamber 10.

[0154] In either of the above-described first and second embodiments,the state after the heating process scarcely changes from the stateafter the pressing process. However, the present invention is notlimited to this feature. For example, it suffices if the state after theheating process, i.e., the state after the hardening reaction of thethermosetting resin is completed, is the state as illustrated in FIGS.11C and 11D, FIGS. 13B and 13C, or FIG. 15B.

[0155] An inkjet head of the present invention is not limited to that ofa line printing type inkjet printer as in the above-describedembodiments in which printing is performed with moving a print paperrelatively to the fixed head main body 2 a. For example, the presentinvention is applicable also to an inkjet head of a serial printing typeinkjet printer in which printing is performed on a print paper with ahead main body reciprocating perpendicularly to the movement of theprint paper.

[0156] Further, an inkjet head of the present invention is not limitedto that of an inkjet printer, For example, the present invention isapplicable also to an inkjet head of an inkjet facsimile or copyingmachine.

[0157] While this invention has been described in conjunction with thespecific embodiments outlined above, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, the preferred embodiments of theinvention as set forth above are intended to be illustrative, notlimiting. Various changes may be made without departing from the spiritand scope of the invention as defined in the following claims.

What is claimed is:
 1. An inkjet head comprising: an ink passage unitincluding a plurality of pressure chambers and a plurality of wallportions defining each of the plurality of pressure chambers; anactuator unit including a piezoelectric element disposed on the inkpassage unit, a surface electrode disposed on the piezoelectric elementand having a main electrode portion opposed to a pressure chamber and aconnecting portion opposed to a wall portion, and a land disposed on thepiezoelectric element in a region opposed to the wall portion, the landbeing electrically connected to the surface electrode; a printed circuitboard on which a terminal electrically connected to the land and apredetermined wiring pattern are provided; a metallic bond forelectrically connecting the land to the terminal, the metallic bondbeing disposed in at least one of a region between the land and theterminal and a region extending over the land and the terminal along theperipheries of the land and the terminal; and a protrusion disposed onthe connecting portion.
 2. The inkjet head according to claim 1, whereinthe protrusion extends to the outside of the connecting portion tosurround the land, the terminal, and the metallic bond.
 3. The inkjethead according to claim 1, wherein the protrusion extends across theconnecting portion substantially perpendicularly to a straight lineextending through the main electrode portion and the land, to theoutside of the connecting portion.
 4. The inkjet head according to claim1, wherein the protrusion connects the actuator unit and the printedcircuit board.
 5. The inkjet head according to claim 1, wherein theprotrusion is made of a thermosetting resin.
 6. The inkjet headaccording to claim 1, wherein the protrusion is made of an epoxy resin.7. The inkjet head according to claim 1, wherein the plurality ofpressure chambers are arranged in a matrix in a plane of the ink passageunit, and the piezoelectric element of the actuator unit has a size toextend over the plurality of pressure chambers.
 8. An inkjet headcomprising: an ink passage unit including a plurality of pressurechambers and a plurality of wall portions defining each of the pluralityof pressure chambers; an actuator unit including a piezoelectric elementdisposed on the ink passage unit, a surface electrode disposed on thepiezoelectric element and having a main electrode portion opposed to apressure chamber and a connecting portion opposed to a wall portion, anda land disposed on the piezoelectric element in a region opposed to thewall portion, the land being electrically connected to the surfaceelectrode; a printed circuit board on which a terminal electricallyconnected to the land and a predetermined wiring pattern are provided; ametallic bond for electrically connecting the land to the terminal, themetallic bond being disposed in at least one of a region between theland and the terminal and a region extending over the land and theterminal along the peripheries of the land and the terminal; and athermosetting resin covering at least part of the metallic bond.
 9. Theinkjet head according to claim 8, wherein the thermosetting resinextends to the outside of the connecting portion to surround the land,the terminal, and the metallic bond.
 10. The inkjet head according toclaim 8, wherein the thermosetting resin extends across the connectingportion substantially perpendicularly to a straight line extendingthrough the main electrode portion and the land, to the outside of theconnecting portion.
 11. The inkjet head according to claim 8, whereinthe thermosetting resin is disposed in a region opposed to the wallportion.
 12. The inkjet head according to claim 8, wherein thethermosetting resin is an epoxy resin.
 13. The inkjet head according toclaim 8, wherein the plurality of pressure chambers are arranged in amatrix in a plane of the ink passage unit, and the piezoelectric elementof the actuator unit has a size to extend over the plurality of pressurechambers.
 14. An inkjet head comprising: an ink passage unit including aplurality of pressure chambers and a plurality of wall portions definingeach of the plurality of pressure chambers; an actuator unit including apiezoelectric element disposed on the ink passage unit, a surfaceelectrode disposed on the piezoelectric element and having a mainelectrode portion opposed to a pressure chamber and a connecting portionopposed to a wall portion, and a land disposed on the piezoelectricelement in a region opposed to the wall portion, the land beingelectrically connected to the surface electrode; a printed circuit boardon which a terminal electrically connected to the land and apredetermined wiring pattern are provided; and a thermosetting resin forelectrically connecting the land to the terminal, the thermosettingresin being disposed in a region opposed to the wall portion.
 15. Theinkjet head according to claim 14, wherein the thermosetting resinextends to the outside of the connecting portion to surround the landand the terminal,
 16. The inkjet head according to claim 14, wherein thethermosetting resin is an ACP (Anisotropic Conductive Paste).
 17. Theinkjet head according to claim 14, wherein the plurality of pressurechambers are arranged in a matrix in a plane of the ink passage unit,and the piezoelectric element of the actuator unit has a size to extendover the plurality of pressure chambers.
 18. A manufacturing method ofan inkjet head comprising an ink passage unit including a plurality ofpressure chambers and a plurality of wall portions defining each of theplurality of pressure chambers; an actuator unit including apiezoelectric element disposed on the ink passage unit, a surfaceelectrode disposed on the piezoelectric element and having a mainelectrode portion opposed to a pressure chamber and a connecting portionopposed to a wall portion, and a land disposed on the piezoelectricelement in a region opposed to the wall portion, the land beingelectrically connected to the surface electrode; and a printed circuitboard on which a terminal electrically connected to the land and apredetermined wiring pattern are provided, the method comprising stepsof: forming a protrusion on the connecting portion; disposing a metallicbond between the terminal and the land; and pressing the land and theterminal so that they are brought near each other, for electricallyconnecting the land and the terminal to each other with the metallicbond being disposed in at least one of a region between the land and theterminal and a region extending over the land and the terminal along theperipheries of the land and the terminal.
 19. The method according toclaim 18, wherein the protrusion is formed so as to extend to theoutside of the connecting portion and surround the land, the terminal,and the metallic bond.
 20. The method according to claim 18, wherein theprotrusion is formed so as to extend across the connecting portionsubstantially perpendicularly to a straight line extending through themain electrode portion and the land, to the outside of the connectingportion.
 21. The method according to claim 18, wherein the protrusion isformed so as to connect the actuator unit and the printed circuit board.22. The method according to claim 18, wherein the protrusion is made ofa thermosetting resin.
 23. The method according to claim 18, wherein theprotrusion is made of an epoxy resin.
 24. The method according to claim18, wherein the plurality of pressure chambers are arranged in a matrixin a plane of the ink passage unit, and lands are provided to correspondto the respective pressure chambers.
 25. A manufacturing method of aninkjet head comprising an ink passage unit including a plurality ofpressure chambers and a plurality of wall portions defining each of theplurality of pressure chambers; an actuator unit including apiezoelectric element disposed on the ink passage unit, a surfaceelectrode disposed on the piezoelectric element and having a mainelectrode portion opposed to a pressure chamber and a connecting portionopposed to a wall portion, and a land disposed on the piezoelectricelement in a region opposed to the wall portion, the land beingelectrically connected to the surface electrode; and a printed circuitboard on which a terminal electrically connected to the land and apredetermined wiring pattern are provided, the method comprising stepsof: disposing a metallic bond and a thermosetting resin between theterminal and the land; pressing the land and the terminal so that theyare brought near each other, for discharging at least part of thethermosetting resin from a gap between the land and the terminal, andbring at least one of the terminal and the metallic bond into contactwith the land; and heating the metallic bond and the thermosetting resinso that the land and the terminal are electrically connected to eachother with the metallic bond being disposed in at least one of a regionbetween the land and the terminal and a region extending over the landand the terminal along the peripheries of the land and the terminal, anda protrusion made of the thermosetting resin is formed at least in theconnecting portion between the main electrode portion and the land. 26.The method according to claim 25, wherein the protrusion is formed so asto extend to the outside of the connecting portion and surround theland, the terminal, and the metallic bond.
 27. The method according toclaim 25, wherein the protrusion is formed so as to extend across theconnecting portion substantially perpendicularly to a straight lineextending through the main electrode portion and the land, to theoutside of the connecting portion.
 28. The method according to claim 25,wherein the protrusion is formed so as to connect the actuator unit andthe printed circuit board.
 29. The method according to claim 25, whereinthe protrusion is made of an epoxy resin.
 30. The method according toclaim 25, wherein the plurality of pressure chambers are arranged in amatrix in a plane of the Ink passage unit, and lands are provided tocorrespond to the respective pressure chambers.
 31. A manufacturingmethod of an inkjet head comprising an ink passage unit including aplurality of pressure chambers and a plurality of wall portions definingeach of the plurality of pressure chambers; an actuator unit including apiezoelectric element disposed on the ink passage unit, a surfaceelectrode disposed on the piezoelectric element and having a mainelectrode portion opposed to a pressure chamber and a connecting portionopposed to a wall portion, and a land disposed on the piezoelectricelement in a region opposed to the wall portion, the land beingelectrically connected to the surface electrode; and a printed circuitboard on which a terminal electrically connected to the land and apredetermined wiring pattern are provided, the method comprising stepsof: disposing a metallic bond and a thermosetting resin between theterminal and the land; pressing the land and the terminal so that theyare brought near each other, for discharging at least part of thethermosetting resin from a gap between the land and the terminal, andbring at least one of the terminal and the metallic bond into contactwith the land; and heating the metallic bond and the thermosetting resinso that the land and the terminal are electrically connected to eachother with the metallic bond being disposed in at least one of a regionbetween the land and the terminal and a region extending over the landand the terminal along the peripheries of the land and the terminal, andat least part of the metallic bond is covered with the thermosettingresin.
 32. The method according to claim 31, wherein the thermosettingresin is formed in the heating step so as to extend to the outside ofthe connecting portion and surround the land, the terminal, and themetallic bond.
 33. The method according to claim 31, wherein thethermosetting resin is formed in the heating step so as to extend acrossthe connecting portion substantially perpendicularly to a straight lineextending through the main electrode portion and the land, to theoutside of the connecting portion.
 34. The method according to claim 31,wherein the thermosetting resin is formed in the heating step in aregion not opposed to the connecting portion.
 35. The method accordingto claim 31, wherein the thermosetting resin is an epoxy resin.
 36. Themethod according to claim 31, wherein the plurality of pressure chambersare arranged in a matrix in a plane of the ink passage unit, and landsare provided to correspond to the respective pressure chambers.
 37. Amanufacturing method of an inkjet head comprising an ink passage unitincluding a plurality of pressure chambers and a plurality of wallportions defining each of the plurality of pressure chambers; anactuator unit including a piezoelectric element disposed on the inkpassage unit, a surface electrode disposed on the piezoelectric elementand having a main electrode portion opposed to a pressure chamber and aconnecting portion opposed to a wall portion, and a land disposed on thepiezoelectric element in a region opposed to the wall portion, the landbeing electrically connected to the surface electrode; and a printedcircuit board on which a terminal electrically connected to the land anda predetermined wiring pattern are provided, the method comprising stepsof: disposing a thermosetting resin between the terminal and the land;pressing the land and the terminal so that they are brought near eachother, for bring at least one of the terminal and the thermosettingresin into contact with the land; and heating the thermosetting resin sothat the land and the terminal are electrically connected to each otherwith the thermosetting resin being disposed in a region opposed to thewall portion.
 38. The method according to claim 37, wherein thethermosetting resin is formed in the heating step so as to extend to theoutside of the connecting portion and surround the land and theterminal.
 39. The method according to claim 36, wherein thethermosetting resin is an ACP (Anisotropic Conductive Paste).
 40. Themethod according to claim 36, wherein the plurality of pressure chambersare arranged in a matrix in a plane of the ink passage unit, and landsare provided to correspond to the respective pressure chambers.